Printer



Dec. 16, 1958 E. A. HILTON ET AL 2,364,307

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.re-cycled to obtain a new set of data.

United States Patent PRINTER Edgar A. Hilton, LosAltos, and Harold F. Elliott, Menlo Park, Califi, assignors to Hewlett-Packard Company, Palo Alto, Calif., a corporation of California Application March 9, E56, Serial No. 570,553

13 Claims. (Cl. fill-93) This invention relates generally to a printer and more particularly to a printer which is especially suitable for printing data such as displayed by electronic counters.

In co-pending application Serial No. 527,907 filed August 12, 1955 and entitled Printing Method and Systern, now abandoned of which this is a continuation-inpart, there is described a printing system which serves to print data which is rep-resented by distinctive data .potentials. The system employs-a printer which is provided with a plurality of type carriers each having a plurality of type characters corresponding to the data. A plurality ofreference potentials are formed each corresponding to a particular type character. The reference potentials are scanned as the print characters are brought into printing position. Coincidence circuits receive the reference and data potentials and generate signals which serve to lock the respective type carrier to thereby .hold the character corresponding to the data in print position. The data is then printed.

A system of the above character is particularly adaptable to printing data such as is displayed on electronic counters, frequency meters, time rate indicators, etc. In general, in these systems the data is displayed for a predetermined interval of time and then the apparatus is A printing mechanism for use with a system of the above character must be capable of rapid operation whereby thedatais printed during the period that the data is displayed.

It -is an object of the present inention to provide a printer which is adaptable for use in systems of the'above character and in which a cycle of operation is of relatively shortduration.

It is another object of the present invention to provide a printer in which the type carriers are carried and driven by a single shaft.

It is another object of the present invention'to provide an electromagnetically-controlled cyclically operated printer which is capable of rap-id positive operation.

It is 'still another object of the present invention to provide an electromagnetically-controlled cyclically operated printer=in which the type carriers are set up during a first portion=of the cycle of operation and impressions grease? appear more clearly from the following description taken in conjunction with the accompanying drawings.

Referring to the drawings:

Figure 1 is a side elevational view of the printer.

Figure 2 is a side view with the cover removed and showing certain of the parts in section.

Figure 3 is a side elevational view of the opposite side of the printer.

Figure 4 is a view taken along the line 44 of Figure 2.

Figure 5 is a partial view taken along the line 55 1 of Figure l and showing the ribbon transport mechanism.

of the characters taken during the second portion of the :Which is compact, and which is relatively simple to'assemble and'maintain.

7 It is still another object of the present invention to provide a printer in which the speed of operationdoes not depend upon the number of digits in thedata, and in-which any predetermined number of digits mayfbe Supplied.

These and other objects of the present invention will serves to rotatably mount the carriers.

Figure 6 shows a commutator suitable for deriving reference potentials.

Figure 7 is a plan view of a brush which may be employed to scan the'commutator of Figure 6.

Figure 8 is a side elevational view of the brush of Figure 7.

Figure 9 is a side elevation View in section of a type carrier assembly showing the commutator and brush and driving means.

Figure 10 shows suitable means for forming a reference potential for application to the commutator.

Figure 11 shows a circuit suitable for operating the electromagnetically operated clutch.

Figure 12 shows a suitable coincidence circuit which may be employed in conjunction with the printing mechanism and :which serves to provide signals for locking the type carriers. i

Figure 13 is a block diagram of a printing system in which the printer may be employed.

Figures l4a-l4g show the sequence of operation-of the printer.

In general, the printer serves to print data which may be represented by distinctive source potentials. One source of such potential may, for example, be an electronic counter. Counters of this type display the data fora predetermined interval of time. They also generate a voltage which is distinctive of the displayed count.

The printer is provided with a plurality of type carriers or wheels, each carrying a plurality of characters corresponding to the data to be printed. A power shaft Friction drive means is associated with each of the type carriers or wheels and serves to transmit power from the shaft to the respective carrier. A plurality of commutators, one for each of the type carriers, are provided. Each of the commutators has a plurality of contacts, the number corresponding to the number of type characters carried by the carriers. Means are provided for applying a dis tinctive reference potential to each of the contacts. A sensing means is associated with each of the type carriers and is adapted to rotate therewith. The sensing means serves to sense the potential at each of the contacts sequentially as the carriers are rotated by the shaft.

The sensed potential is indicative of the character in printing position.

A plurality of electromagnetic means, one for each of the type carriers, serves to lock the associated type carrier or Wheel against rotation when the character corresponding to that digit of the data. is inprint position. These electromagnetic means are controlled through :a suitableicircuit, for example, a coincidence circuit of the to lock the type carriers.-

An electromagnetically controlled clutch serves to cyclically apply power to the printer. During eachcycle '3 of operation of the clutch, the power shaft is rotated. During the first portion of the cycle of operation the type carriers are set up or locked to bring all of them in line in printing position. During the second portion of the cycle of operation, an impression of the characters in print position is taken to give a printed record of the data displayed by the counter. Means are also provided for cyclically advancing the paper past the printing platen.

Referring now particularly to Figures 1, 2 and 3, a suitable electromagnetically-controlled means for supplying power to the printer is shown. A motor (not shown) serves to rotate the shaft 11 which carries the gear 12. The motor, for example, may be any suitable alternating or direct current motor which has suflicient power to operate the printer. The motor serves to continuously rotate the gear or-pulley 12 which drives the belt 13. The belt 13 engages a second pulley 14 which is rotatably mounted on the shaft 16 and adapted to slide axially withrespect thereto. A clutch plate 17 (Figure 4) is mounted on the pulley 14. The clutch plate carries a plurality of teeth 18 on its face. These teeth are adapted to engage the teeth 19 formed on the driven clutch plate 21. The driven clutch plate 21 is suitably secured to the gear 22 and serves to drive the gear 22 and shaft 16 when the clutch is engaged, i. e., when the teeth 18 and 19 are mated.

A hub 23 having a-groove 24 formed therein is suitably secured to the pulley 14 and is adapted to rotate therewith. The fork 26 carries a pair of rollers 27 and 28 which are adapted to ride in the groove 24. The fork 26 is suitably pivoted on the pin 29 which is carried by the brackets 31 which are suitably secured to the side plate 33 as, for example, by means of screws 34 and 36. The upper member 38 of the fork 26 has a portion 39 (Figure 4) at right angles thereto and which extends through an accommodating slot formed in the side plate 33. The arm 39 engages with the arm 41 mounted on the shaft 42. A spring 43 is suitably mounted on the side plate 33, for example, it may be riveted 44 to the side plate 33. The spring 43 urges the arm 39 towards the rear of the printing mechanism whereby the fork 26 is pivoted towards the member 33 to urge the driving plate of the clutch into engagement with the driven plate.

The arm 41 is adapted to rotate with the shaft 42. The arm 41 may, for example, be attached to the collar 47 which is then secured to the shaft 42 by a set screw 48. The shaft 42 is journalled on the Ushaped member 49 which is attached to the bracket 51 which is suitably secured to the side plates 33 and 52. The length of the shaft is such that lateral movement thereof is prevented by the side plates 33 and 52. An armature 53 is suitably attached to the shaft 42. For example, the armature maybe secured to the shaft 42 by means of the screws 54 and 56. A coil 57 is carried by the U-shaped member 49 and is attached thereto. A magnetic core 58 is disposed within the coil 57.

Operation of the electromagnetically-controlled clutch is as follows: As shown in Figure 2, the clutch is engaged (Figure 4) and power is being transmitted to the printer. The shaft 16 is rotated. As the shaft 16 rotates through one revolution, the cam member 61 which is attached for rotation therewith, for example, by means of set screw 62 rotates through a revolution. The member 61 carries a pair of cam surfaces 63 and 64 which engage the upturned portions 66 of the armature. Thus, as the shaft 16 rotates through one revolution, the cams 63 and 64 cam the armature downward in the direction indicated by the arrow 67. This brings the armature into contact with the magnetic core 58. When the coil 57 is energized, the magnetic force is sutficient to hold the armature down against the tension of the spring 43. When the coil 57 is de-energized, the armature 53 is released thereby allowing the spring 43 to urge the arm 41 toward the back of the printer wherebythe clutch is engaged for a cycle of operation. Thus, it is seen that I have provided electromagnetic means which serves to control engagement of the clutch. The clutch is operated by de-energizing the coil. The camming action of the cams to urge the armature in contact with the core 58 serves to make practicable the use of the electromagnetic means in which the power requirements are at a minimum.

The gear 22 is attached to the driven clutch member and engages the idler gear 71 which drives the gear 72 mounted on the power shaft 73 which carries and drives the type carriers.

Referring particularly to Figures 4 and 9, a plurality of type carriers are shown mounted on the power shaft 73. The type carriers 76 have a circular groove 77 which carries a brush, to be presently described, and a circular groove 78 which carries a friction driving disc. Each of the type carriers 76 are rotatably mounted on a bushing 79 which makes a slip fit with the shaft 73. A spring washer 81 is adapted to fit over the shaft and have its inner portion engaged by the end faces of bushings 79.- The face 82 bears against the friction driving disc 83. A nut 85 is threaded onto the end of the shaft and serves to apply axial pressure to the bushings whereby the inner portion 84 of washers 81 is locked between. bushings. The shaft, washers and bushings then rotate together. Friction betweenthe faces 82 of the washers 81 and the discs 83 rotates the type carriers. The fric-' tion is such that the type carriers may be locked against rotation, as will be presently described, and the shaft, bushings and washers may continue to rotate.

Each of the type carriers serves to carry a plurality of characters 86 (Figures 2 and 9) on its outer peripheral face. As previously described, these characters may be numbers or other suitable characters which represent the data to be printed. Between characters 86 there is a detent portion 87. This detent portion is employed to lock the characters when the characters to be printed are in printing position. Referring particularly to Figure 2, the arrow 88 indicates the direction of rotation of the type carriers. A plurality of armatures 89, one for each print carrier, are located on the upper side of the printing mechanism and attached to the case by a suitable bracket 91 which extends across and is fixed to the side members 33 and 52.

Each of the armatures 89 is in the form of a spring, which has a normal position which is as shown in the figure. Electromagnetic means 92 are associated with each one of the armature members 89. Thus, when the electromagnetic coil 92 is energized, the core 93 becomes suitably magnetized to draw the respective armature upwards. When the electromagnetic means is de-energized, the armature moves downward whereby the end portion 94 falls into one of the detents 87 and abuts against the adjacent face of the type character thereby locking the wheel against further rotation. A circuit, to be presently described, is employed for controlling application of electric energy to the various coils 92.

Suitable means are provided for sensing and relaying the information relative to the character in print position. Thus, a plurality of cornrnutators 96, one corresponding to each of the type carrier wheels are disposed between type carriers. Referring particularly to Figure 9, a pair of commutators are shown arranged between wheels. The type wheel carries a brush which rides on the contact elements of the commutator and connects it to an external circuit. Thus, as the type carrier is rotated, the brush rotates therewith and contacts with the contacts of the armature to transmit a voltage which corresponds to the type carrier in print position.

Referring now to Figures8 and 9, a brush 97 which is attached to a washer 98 rides in the groove 77. The washer is adapted to tightly fit into the groove whereby the brush rotates with the type carrier. The brush shown in the figures comprises an annular member having portions 99 and 100 formed as segments thereof. These 'nals 1060-1061.

between the members 128 and 129.

portions act "as the brush element and are connected at their ends 101 and 102. The brush 97 is bentas :shown in Figure 8 to provide pressure between the brushiand the commutator elements withwhich it is in contact.

the wheel if desired.

The commutator96 (Figure 6) is formed with a plurality 'of contacts tuna-105;, the number of segments corresponding to the number'of print characters carried by'the type carrier 76. Suitable-means are provided for making an electrical connection to the various contacts 103. Referring particularly'to Figure .6, the contacts 1-936Z-103j are connected by the conductors tothetermi- The annularmember 108 is concentric with the plurality of contacts 103a-103j and is conductively connected to'the terminal 109.

The annular member has a plurality of projections or ears 111 disposed between the contacts. Thus, as the brushes99 and 100 rideoverthe contact elements 1113a- 103 and the ring 108, the segments aresuccessively connected to the ring. If the.ears'1 11 were notpresent, the brush elements 99 and 100 would bounce. If a predetermined voltage is :applied to each of the terminals 106a-1il6jjthis voltage 'is successively commutated to the terminal 109 where it is available to indicate the-position of the resp'ective type carrier.

Referring to Figure 2, suitable means are provided for advancing paper 121 between the printing bar or platen 122 and the typecarriers 76. Thus, the paper 121 ipasses betweenthe upper guide 123.and the lower'guide 124. The guides-123 and :124 are suitably attached to the plate 141. The paper "passes between the paper advancer rollers 126 and 127, between. a second pair of guides 123 and 129,past the printing bar 122 and thence through the "opening 131. The upper guide 128 has apair of finger-like members 132 and 133 (Figure 4) which are adap'tedto ride in the' grooves 134and 136 of roller 126. The lower member- 129 similarily has a pair of fingers 137which ride in accommodating grooves 138. These fingers serve to guide the paper into the openingrformed The rollers 126 and 127 may be formed of any suitable-material. For example, they may be formed of soft rubber which'will frictionally engage and advance the .paper. The roller 127 is mounted on a shaft 139. The shaft'139 is jour- -nalled on a pair of spaced arms'141 and 142 (not shown), which are spring-loaded. The arms are pivoted 143 on the side plates 33 and52. The'spring 144 urges the roller 127 against the roller 126. The spring is mounted between the arms 141-and the pins 146 which are suitably secured to the respective side plate.

The roller 126 is mounted on the shaft 151 and extends through the side plates 33 and 52. The end which extendsthrough the side 33 is provided with a suitable knob (not shown) for manually advancing the paper.

The other end is provided with means for advancing the by a loclo'n screw 157. A roller 158 is mounted on the arm andis adapted to ride on the cam 153. The

rm 11 9 is pivoted 161 to the side frame 52. An aim 162 is pivotally connected 163 to the arm 159. A spring 164 is connected between the projection v166 of the arm-162 and a pin 167 which is attached to the side frame member 52; The spring 164 provides a force which-keeps the roller 15% in continuous contact with the cam :surface. The forward end of the arm 162 is provided-With a hoololike portion 168. This portion, is

' The gear 211 is provided with a collar 213.

which is pivoted 178 to-the side member 52.

E adapted to engage the teeth 169 formed on the vwheel 17.1. The wheel 171is suitably attached to the shaft 1'51 to thereby rotate thesame.

As the shaft 16 is rotated through one revolution, -the=arm 159 is-caused to pivot about the point 161 drawing the hook-like member 168 in such a direction that the wheel 171 isrotated a predetermined amount, which depends upon the-spacing 'of the teeth and the length of the arm 15h. The forward portion of the arm 162 is accommodated by a guide 172 which is suitably attached by means of screws 173 to the side frame member. Rotation of the wheel 171 causesrotation :of the shaft 151 which rotates the .roller 126. As previously. described, the roller 126 rotates in the direction shown by the arrow 174 and servesto advance the paper.

The tooth-like members 169'also act as detents. Thus, the roller 176 is mounted on .one end of the arm 177 The other end of the arm is engaged by the spring 179 which 'has its free endattached to the pin 181 secured to the side member 52. Thus, as the wheel 171 advances through a predetermined angleof rotation, the action of the roller 176 with the teeth 1'69 serves to exactly position the wheel 171. Whenthehook-like member 168iis advanced downwardly, itwill positively engage a tooth.

Means are provided fortaking the impression -of'the character in print position. The'paper whichis employed may carry its own carbon paper whereby whenthe platen 122 provides pressure between the paper and the. print characte 'the character is transferred onto the paper. However, we prefer to use a ribbon which moves between the paper and the print character and which serves to transfer the character ontothe paper. The ribbon may be of the type which isused in typewriters. The

. ribbon carrying and advancingmechanism is shown in Figure 5. A pair ofspools 183 and 134, one located I on each side of the printing'mechanism, are employed to carry the ribbon. The spools are mounted "on the shafts 186 and 187, respectively, and held thereon'by the spring members 188 and 189. The ribbon-passes 'over'the guides 191 and192. It is then twisted through and passes over the guide 193 laterally through the printer between the print carriers and paper, as shown in Figure 1, and then over'a complementary set of rollers. These rollers are shown in Figure 5 and are labelled 194, and 196.

The roller 191 is mounted on an 197 which is pivoted on the shaft 186. Spring 1% is mounted between the'pins 199 and 2111. The pin 199 is mounted on the arm 197 and the pin 2110 is mounted on the side plate 33. The action of'the spring 198 is to urge the arm in a direction to maintain the ribbon in tension. Associated with shaft 187 is a second arm The spring 2113 ismounted between pins 219% and 266 (not shown). The pin 204 is mounted on the arm 292 while the pin'2fi6 is mounted on the side frame 52. Again the spring tends to urge the arm in a direction to maintain the tape in tension.

A gear 208 is mounted on the shaft 151 for rotation therewith. The gear 203 is engaged with a gear 2119 which is mounted on the shaft 139 to drive the roller 127 and which also drives the gear 211 mounted on the shaft 212. Suitable means are provided for locking the gear to the shaft-212, for example, the lock screw 214 may be employed. A second gear 216 is mounted on the other end of the shaft 212 for conjoint rotation therewith. The gear 216 is adapted to engage the gear 221 which is mounted on the shaft 136 and adapted to rotate the same. The ree1183 is removably mounted on the shaft 186 and adapted to'be rotated by the same. The gear 211is adaptedto engage with the gear 222 and to. drive the associated removable reel 184 through the shaft 187. V

The shaft 212 is journalled on the side frame members 33 and 52, and adapted to move transversely with respect I the opposite side of the apparatus and pivoted on the 7 thereto whereby either the gear 216 or gear 211 is engaged with its associated driven gear 221 or 222. This arrangement permits driving either of the reels, as will be presently described.

A suitable arrangement is provided for moving the shaft 212 transversely to engage the appropriate pair of gears. This arrangement may comprise a pair of arms 223 and 224 which are pivoted on the member 226 at the points 227 and 228, respectively. A member 229 is pivotally connected to the ends 231 and 232 of the arms 223 and 224, respectively. The other ends of the arms 233 and 234 are suitably connected to a pair of springs 236 and 237, respectively. For example, the spring may be attached to the arms by means of pins 238 and 239. The other end of the spring is mounted on a pin 241 which is fixed to the member 226. The springs are so arranged that the arms are adapted to assume one of two positions. Thus, as illustrated, the arms are rotated counterclockwise and urged in this direction by the action of the springs 236 and 237. By rotating the arms in a clockwise direction they will assume a second position of rest and be urged clockwise by the springs. This is achieved by properly locating the pin 241 whereby the action of the spring in the two positions is to rotate the associated arms in the respective directions. The arms engage the collars 242 and 243 to urge the shaft 212 transversely of the printer. In the direction shown, the end of the arm 224 engages the roller 242 to urge the gear 211 out of engagement with the gear 222 and the gear 216 into engagement with the gear 221. In this position, the reel 183 acts as a take-up reel. When the ribbon is completely unwound from the reel 184, the tension of the tape will rotate the arm 202. The end of the arm 202 engages with the end 233 of the arm 223 and serves to rotate the same in a clockwise direction. The other end of the arm 223 then engages the collar 243 to urge the shaft 212 transversely whereby the gear 211 engages the gear 222, and the gear 216 is disengaged from the gear 221. The springs 236 and 237 then act to maintain the gear 211 in engagement. Thus, in this way the reel 184 becomes the take-up reel while the reel 183 becomes the supply reel. When the supply reel 183 is completely unwound, it will urge the arm 197 in such a direction as to disengage the gear 211 and engage the gear 218. Thus it is seen that I have provided an arrangement in which the function of the reels is automatically interchanged as all of the tape is fed from one to the other.

The gearing may be such that the shaft 73 which carries the type wheels or carriers rotates through two revolutions, while the shaft 16 undergoes a single revolution for a cycle of operation. During the first revolution of the shaft 73, each of the type carriers is locked in position whereby the appropriate print character is in the print position. During the second revolution, the printing bar is urged upward to print the characters in printing position. This is accomplished by means of the pair of arms which are located at opposite ends of the print bar and which are pivotally mounted on the shaft 151. It is, of course, apparent that different gearing may be employed. Thus, during the first portion of a cycle the carriers are locked and during the second portion a print is made.

Referring particularly to Figure 2, the arm 251 which is mounted inside the side plate 52 is shown. A similar arm is mounted just inside the side plate 33 and operates in the same manner. The arm 251 has a roller 252 mounted at one end thereof. The arm is engaged by a spring 253 which is mounted on the pin 254 mounted on the side frame 52. The spring 253 urges the roller 252 into contact with the earn 256. The printing bar or platen is mounted on the other end of the arms 251. Thus when the shaft 16 rotates through one revolution, the cam 256 urges the arm in such a direction that when the roller reaches the point 257 the printing bar is moved to print the characters in printing position. Although I have described a single arm 251 with associated cams and rollers,

8 it is to be understood that a similar arrangement is located on the opposite side of the printer.

The paper may be carried by a roll 261 which is mounted on the shaft 262, or the paper may be folded and laid on the bottom plate.

A suitable circuit for forming reference voltages for application to the contacts 103a-103i is shown in Figure 10. A voltage E is applied across the series resistors 271-279. Leads are connected to the ends of the series combination and to the common junction of each of the registers. The leads 281a-28lj are adapted to be connected to the terminals 106a-106i. The potential appearing at each of these leads depends upon its position along the series combination. Thus, the voltages applied to the contact members 103a-103j will increase step-wise in a clockwise direction. When these contacts are scanned clockwise by the brushes 99 and 100, the voltage which appears at the terminal 109 will be an increasing step voltage, the particular voltage depending upon the angular position of the type carriers.

As previously described, the printer may be used to print any data which is represented by distinctive potentials. For purposes of illustration only, it will be described with reference to electronic counters. In electronic counters the unknown frequently is applied to the counting circuits when a gate is opened. When the gate closes, the counting circuits display the count for a predetermined controllable period of time. The counting circuits are then reset to zero and the gate is opened for the next count. In general, apparatus of this type may be adapted to provide a plurality of output or source potentials which are indicative of the value of each digit of the count.

As previously described, the printer is adapted to print during the interval that the gate is closed and the count is being displayed. This is accomplished by employing the pulse which serves to close the gate at the completion of the count to de-energize the coil 57 which holds the armature 53. As previously described, this initiates a print cycle.

A suitable circuit for de-energizing the electromagnetic means in response to a pulse is shown in Figure 11. The RC circuit composed of resistor 286 and capacitor 287 serves to apply a negative pulse to the control grid 288 of the tetrode 289. The screen grid 291 is connected to a source of screen voltage +V. Plate voltage is applied to the terminals 292 and 293. The coil 57 of the electromagnetic clutch is connected in the plate circuit. The operating voltages are selected whereby the tube is continuously conducting to keep the electromagnetic means energized. When the gate closes, the RC network develops a negative spike which momentarily cuts off the tube. At this instance, the coil is de-energized and the armature 53 is released whereby the clutch is engaged to drive the printer through one cycle of operation. The tube goes immediately back into conduction whereby the coil 57 is re-energized to engage and hold the armature when it is cammed downward by the earns 63 and 64.

As previously described, the print characters are locked in a printing position when the electromagnetic means 93 is de-energized to release the arms 89 and then drops down to engage the members 94 with the associated detens 87 formed on the print carriers. Two coincidence circuits which are suitable for controlling the electromagnetic means are shown and described in said co-pending application. These circuits serve to de-energize the electrornagnetic means when the source and reference potentials have a predetermined relationship. One of the circuits described in said copending application is shown in Figure 12.

The circuit in Figure 12 operates on a carrier frequency principle. It comprises a first amplifier tube 301, triode 302 connected as a detector, and a second amplifier 303. A suitable D. C. voltage is applied to the screen grid 304 of the tube 301. A carrier signal is applied to the con t'rol grid 306 through the resistor 307. The input signal which is derived by combining the source and reference potential, as will be presently described, is also applied to the grid 306 through the resistor 308. The plate of the tube 301 is connected to a plate supply voltage through the resistor 309. The plate is also connected to the line 311 through the series combination capacitor 312 and resistor 313; The suppressor grid is directly connected to the cathode and to line 311. The cathode of the triode 302 is connected to the common junction of the capacitor 312 and resistor 313. The plate and grid of the tube 302 areconnected together and to the line 311 through the parallel combination of capacitor 314 and resistor 315. The control grid 317 of the amplifier tube 303 is connected to the plate ofthe tube 302. The screen grid is connected to the platesupply voltage through the resistor 318. The suppressor grid is connected to the cathode and to line 311. The plate is connected to the electromagnetic means 92 and serves to provide current to the coils of the same.

The voltages applied to the elements of the tube 301 are such that the tube does not amplify the carrier signal until the reference and source voltages are coincident (have a predetermined relationship). When the voltages are coincident the tube 301 amplifies the carrier signal and the amplified signal is applied to the triode 302 connected as a detector. The detected signal is applied to the grid 317 to cut off the tube 303. The associated electromagnetic means 92 are de-energized and the arms 89 drop whereby the end portion 94 of each engages the detent formed in the associated type carrier and serves to lock the same against rotation. It is noted that when the type carriers are locked in position, the circuits are coincident and all of the'electromagnetic means 92 remain de-energized. Each electromagnetic means is again energized during the next cycle of operation of the printer if the data associated therewith has changed.

In certain equipment, the reference and source voltages may vary between different limits. It is desirable to provide a suitable mixing circuit for the reference and source potentials. A suitable circuit which comprises a series combination of resistors with suitable taps is described in said copending application.

Operation ofthe printer in a system will be more clearly understood with reference to Figures 13 and 14. Referring particularly to Figure 13, which is a block diagram of a printing system, the electronic counter 321, which may include a plurality of decade counters connected in cascade, is shown connected to associated coincidence means 322-325 through lines 327-4330. The printer 331 supplies a plurality of reference potentials, which correspond to the print character in printing position, to the coincidence means 322-325 along lines 332- 335. A signal is-applied by each of the coincidence means to the associated electromagnetic means 92 of the printer along lines 337-340. The signal from each of the coin cidence means serves to selectively lock the associated type carrier whereby the data represented by the counter 321 is printed when the printing bar is cammed. The gate voltage which initiates the print cycle is applied to the printer along the line 342.

' Referring particularly to Figure 14, the time sequence of operation is graphically illustrated. Curve 14a shows the gate voltage As previously described, the gate is opened for apredetermined period of time. The gate is then closed. When the gate is closed, the count is displayed by the counter. The plurality of source voltages which correspond to the data displayed by the counter are available at the counter. These are applied to the coincidence means 322-325. Figure 14b shows the pulse which is applied to the grid 288 of the tube 289. As previously described, the RC network develops a spike which serves to cut off the tube whereby the clutch is engaged, Figure 140.

The printer then undergoes a complete cycle of oper- 10 ation before the clutch drive and driven members are disengaged by the action of the earns 63 and 64 against the armature 53. During the first half of the printing cycle the shaft 73 rotates through one revolution and the type carriers are set up, Figure 14d, and locked, Fig ure 14g, with the appropriate type character in print position. During the second half of the cycle the roller 2S7 is-engaged to'pivot the arm 251 to urge the printing bar or platen upward to print the data. Shortly thereafter the ribbon and paper are advanced, Figure 14f. This makes the data available immediately after it is printed. Each of the plurality of type carriers is operated upon in the manner described. The description was limited, inparts, to a single carrier to simplify the discussion.

We claim:

1. A printer which serves to print data which is represented by a plurality of data potentials comprising power means, 'a driven shaft, an electromagnetically controlled clutch serving'to cyclically drive said shaft, a plurality of type wheels each having a plurality of print characters rotatably carried in side-by-side relationship on said.

shaft, means associated with each of said wheels serving to drive the same, a commutator having a plurality of contacts disposed adjacent each of said wheels, means for applying reference potentials to the contacts, sensing; meansassociated with each of said Wheels and adapted. to rotate therewith and serving to make contact with the: associated commutator to sense the reference potentials to indicate the character in print position, electromagnetic means associated with each of the type carriers serving to selectively lock the associated carriers when the print character corresponding to the data is in print position, and means for taking an impression of the characters in print position.

2. A printer of the type which serves to print data which is represented by a plurality of potentials comprising a plurality of type carriers one for each digit of the data, each carrier serving to carry a plurality of type characters, a driven shaft serving to rotatably mount said type carriers in side-by-side relationship, friction means associated with each of said type carriers, drive means associated with each type carrier and with said shaft and adapted to be driven by the shaft, said drive means serving to engage the friction means to drive said carriers, a commutator associated with each carrier having a plurality of contacts one for each type character of the associated type carrier, means for applying a distinctivepotential to each of said contacts, sensing means associated with each type carrier and adapted to .be rotated therewith, said sensing means serving to sense the potential of each of said contacts individually and sequentially as the type carrier rotates, the sensed potentials being: indicative of the character in printing position, a pith rality of electromagnetic means one for each type carrier serving to lock the associated type carrier when the typecharacter corresponding to the data is in print position, an el'ectro-rnagnetically controlled clutch serving to-"cyclically drive the printer, said type carriers being locked during the first portion of a cycle and remaining locked. through the remainder of the cycle of operation, and means serving to take an impression of the characters in. print position during the'second portion ofthe cycle of' operation. ii

3. Apparatus as in claim 2 in which said driven shaft undergoes two revolutions during each cycle of operation,

and wherein said type carriers are locked during the first revolution and an impression is taken during the second revolution.

sented by a plurality of data potentials comprising a driven shaft, a plurality of type wheels rotatably carried in side-by-side relationship on said shaft, each of said wheels carrying a plurality of print characters, each of said wheels serving to carry a friction disk, a plurality of drive rings each engaging one of said friction disks carried by said shaft and adapted to rotate conjointly therewith, the drive rings serving to frictionally drive the disks and associated wheels, commutating means associated with each of said wheels and serving to derive a potential indicative of the character in print position, electromagnetic means serving to selectively lock each of the type carriers, and means for taking an impression of the characters in print position.

6. A printer which serves to print data which is represented by a plurality of data potentials comprising a driven shaft, a plurality of type wheels rotatably carried in side-by-side relationship on said shaft, each of said wheels carrying a plurality of print characters, a drive disk carried by each of said type wheels, a plurality of drive rings one disposed adjacent to each of said type wheels and adapted to engage the adjacent drive disk, each of said rings being mounted for conjoint rotation with the shaft, said rings serving to frictionally drive the drive disks and wheels, sensing means carried by each of said wheels, a commutator disposed adjacent said sensing means and having a plurality of potentials applied thereto, said sensing means and commutator serving to develop potentials which are indicative of the character in print position, electromagnetic means serving to selectively lock each of the type carriers, and means for taking an impression of the characters in print position.

7. A printer as in claim 6 wherein said commutator has a plurality of spaced contacts arranged on a circle, said commutator being mounted coaxially with the associated wheel, a circular ring disposed adjacent said contacts and concentric therewith, said sensing means being adapted to ride on said ring and individual ones of said contacts to thereby electrically connect the successive ones of the contacts to the ring.

8. Apparatus as in claim 7 wherein said circular ring disposed adjacent the contacts and concentric therewith has a plurality of finger-like elements formed integral therewith and extending radially outward between said contacts.

9. A printer which serves to print data which is represented by a plurality of data potentials comprising a driven shaft, a plurality of type wheels rotatably carried in side-by-side relationship on said shaft, each of said wheels carrying a plurality of print characters, means associated with each of said wheels for frictionally driving the same, commutating means associated with each of said wheels serving to derive a potential indicative of the character in print position, and electromagnetic means serving to selectively lock each of the type carriers.

10. A printer which serves to print data which is represented by a plurality of data potentials comprising power means, a driven shaft, an electromagnetically controlled clutch serving to cyclically connect said shaft to the power means, a plurality of type wheels each having a plurality of print characters rotatably carried in side-byside relationship on said shaft, means associated with each of said wheels serving to drive the same, a commutator having a plurality of contacts disposed adjacent each of said wheels, means for applying reference potentials to the contacts, sensing means associated with each of said wheels and adapted to make contact with the associated commutator to sense the reference potentials to indicate the character in print position, and electromagnetic means associated with each of said type carriers serving to selectively lock the associated carriers when the print character corresponding to the data is in print position.

11. A printer which serves to print data which is represented by a plurality of data potentials comprising power means, a plurality of type carrying members each serving to carry a plurality of print characters disposed in side-byside relationship, means associated with each of said type carriers for driving the same to bring the print characters successively into printing position, a commutator having a plurality of contacts disposed adjacent each of said type carriers, means for applying reference potentials to the contacts, sensing means associated with each of said type carriers and adapted to move therewith and serving'to make contact with an associated commutator to sense the reference potential and indicate the character in printing position, electromagnetic means associated with each of the type carriers serving to selectively lock the associated carrier when the print character corresponding to the data is in print position, and means for taking an impression of the character in print position.

12. A printer of the type which serves to print data comprising a plurality of type carriers one for each digit of the data, each carrier serving to carry a plurality of type characters, a driven shaft serving to rotatably mount said type carriers in side-by-side relationship, friction means associated with each of said carriers, drive means associated with each type carrier and with said shaft and adapted to be driven by the shaft, said drive means serving to engage the friction means to drive said carriers, a commutator associated with each carrier having a plurality of contacts one for each type character of the associated type carrier, sensing means associated with each type carrier and adapted to rotate therewith, said sensing means serving to sense the potential at each of said contacts individually and sequentially as the carrier rotates, means for receiving said sensed potential and developing a control signal, a plurality of electromagnetic means one for each type carrier connected to receive said control signal and serving to selectively lock the associated type carrier when the type character corresponding to the data is in print position, and means for cyclically driving the printer, said type carriers being locked during the first portion of a cycle and remaining locked through the remainder of the cycle of operation, and means serving to take an impression of the characters in print position during the second portion of the cycle of operation.

13. Apparatus as in claim 12 in which said commutator comprises a plurality of spaced contacts lying on a circle, and a concentric ring disposed adjacent thereto, said sensing means comprising a brush adapted to engage one of said contacts and said ring to successively connect the, contacts to the ring.

References Cited in the file of this patent UNITED STATES PATENTS 1,675,969 Bull July 3, 1928 1,909,550 Pierce May 16, 1933 2,066,748 Tauschek Jan. 5, 1937 2,133,865 .La Boiteaux Oct. 18, 1938 2,157,035 Torkelson May 2, 1939 2,381,862 Beattie Aug. 14, 1945 

